<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8"/>
    <title>v-on:keydown</title>
    <script src="../js/vuejs-2.5.16.js"></script>
</head>

<body>
<div id="app">
    <input type="text" v-on:keydown="fun($event)"><br>
    <input type="text" onkeydown="showKeyCode()">
</div>
</body>
<script>
    //view model
    new Vue({
        el: "#app",
        methods: {
            fun: function (event) {
                var keyCode = event.keyCode;
                if (keyCode < 48 || keyCode > 57) {
                    //让按键不起作用
                    event.preventDefault();
                }
            }
        }
    })
    
    function showKeyCode() {
        var keyCode = event.keyCode;
        if (keyCode < 48 || keyCode > 57) {
            //让按键不起作用
            event.preventDefault();
        }
    }
</script>


</html>